The purpose of the proposed investigation is to secure relevant information concerning the role of the divalent cation in the reaction(s) of estrogen sulfotransferase derived from bovine adrenals and from human breast carcinoma cells in tissue culture (MCF-7). MCF-7 is a human breast cancer line established at this Foundation from a malignant pleural effusion in a postmenopausal woman with metastatic breast cancer. To secure this information, we will utilize nuclear magnetic relaxation and electron spin resonance techniques in conjunction with paramagnetic probes. It is expected that these studies will provide important information regarding the conformation of the enzyme and the dynamics at the active site.